Sulfoalkyl cellulose ethers and their salts as hydraulic natural cement set retarders



June 1l, 1957 H. H. KAVELER 2,795,508

suLEoAExYx. cELLuLosE ETHERs AND THEIR sALTs As HYDRAULIC NATURAL CEMENTsET RETARnERs Filed Aug. 22. 1952 3 Sheets-Sheet 1 CEMENT SLC.

INVHVTOR.

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H.H.KAVELER ATT #EVS June 1l, 1957 H. KAVELER 2,795,508

SULFOALKYL CELLULGS ETHERS AND THEIR SALTS As HYDRAULIC NATURAL. CEMENTSET RETARDERS 1952 3 SheetsFSheet 2 Fm'd Aug. 22

INVHVTOR.

H.H.KAVELER ATT Rl/EYS June 11, 1957 H. H. KAVELER 2,795,508

SULFOALKYL CELLULOSE ETHERS AND THEIR SALTS AS HYDRAULIC NATURAL CEMENTSET RETARDERS Filed Aug. 22, 1952 3 Sheets-Sheet 3 2,795,508 PatentedJune l1, 1957 SULFOALKYL CELLULOSE ETHERS AND THEIR SALTS AS HYDRAULICNATURAL CEMENT SET RETARDERS Herman H. Kaveler, Bartlesville, Okla.,assignor t0 Phillips Petroleum Company, a corporation of DelawareApplication August 22, 1952, Serial No. 305,823

8 Claims. (Cl. 106-93) This invention relates to cements having retardedrates of hydration or set, to slurries of such cement, and to the methodof making these slurries. The cement with which the invention isconcerned is preferably a Portland or Portland-type cement. ln anotheraspect it relates to any hydraulic natural cement composition in a dryform, or with added water in an aqueous slurry form, which when in theform of an aqueous slurry has a retarded initial set or extended orretarded thickening time and/ or a reduced water-loss to adjacent porousformations, due to the addition of a minor but effective amount of acidsulfoalkyl cellulose ethers and salts of the same selected from thegroup consisting of acid a-methylsulfomethyl cellulose ether, acidsulfoethyl cellulose ether, acid sulfopropyl cellulose ether, acid2-methyl-2-sulfoethyl cellulose ether, and acid a,adimethylsulfomethylcellulose ether hereinafter referred to as said list ofsulfoalkylcelluloses" in order to save time, this invention relatingfirst to said compositions of matter, second to processes of compoundingsaid compositions, and third to processes for using said compositions inthe arts of cementing wells, sealing porous formations during thedrilling of wells, cementing casings in the well, squeeze cementing,plugging the well or the earth formation adjacent the same, and groutingor sealing crevices, cracks or holes in manmade formations, such asbuildings, foundations, dams, breakwaters or concrete and masonrystructures, in some instances the cracks or fractures already existingbefore the slurry is pumped into them, and in some cases the pressure ofthe slurry being pumped into or against the surface of said formation orstructure forming by its pressure the cracks or fractures to be filled.

The present application is a continuation-in-part of my copending U. S.patent application Serial No. 47,555

of Herman H. Kaveler, filed September 2, 1948, for Retarded Cement andMethod of Making, now abandoned.

Among the objects of the invention is the provision of a cement having aretarded rate of hydration, or retarded set, as it will be hereinaftertermed, particularly at elevated temperatures up to and above 300 F.and/or at high pressures up to and above 20,000 pounds per square inch,such as are encountered in cementing of deep Wells.

One object of the present invention is to provide a suitable hydraulicnatural cement aqueous slurry, and suitable processes employing thesame, for cementing casing in wells, for squeeze cementing in wells, andfor grouting cracks, fractures or voids, in natural formations, such asin wells, or in man-made formations such as dams, breakwaters, walls andmassive foundations and structures of all types.

Another object of this invention is to provide a dry hydraulic naturalcement powder which is a novel composition of matter, and which may bemixed with water to form an aqueous cement slurry which is a novelcornposition of matter and which has at least one of the followinguseful properties: a relatively retarded time of initial set, arelatively extended thickening time during which it is pumpable, and/ora relatively low water-loss to porous formations with which it may comein contact during cementing or grouting operations.

Further objects of the invention reside in the provision of a slurry ofthe above cement, and in a method of making such slurry.

These and further objects of the invention will be more readily apparentin the following description.

In the cementing of oil wells it is customary to mix a hydraulic naturalcement, for example a Portland or Portland-type cement, with therequisite amount of water to form a pumpable neat slurry, and to pumpthe mixture into the well and down the hole into the place where it isdesired to have it harden. In present oil well drilling u practice, withwells commonly ranging from 6,000 to 12,000 feet or more in depth, hightemperatures are encountered at the locations which are to be cemented,and relatively long periods of time are often required to pump theslurry into place. Furthermore, in the customary practice of pumping thecement slurry down through the casing and either forcing it out thebottom of the casing and upward around the outer surface of the casing,or through perforations in the lower end of the casing into theformation sought to be sealed, the slurry is required to pass throughnarrow channels and small openings. Successful placement of the slurry,therefore, requires that the slurry shall remain fluid and pumpable athigh temperatures for several hours before it begins to harden. However,after the slurry has been pumped into place, it is desirable to have thehydration or set proceed at a rate at which the slurry will attain itsfinal set and develop considerable strength within a reasonable time,say within a few days. It would be even more desirable to have it attainits final set in about 24 hours but often this is not attainable.

As pointed out in the preceding paragraph, the most important functionof the hydraulic natural cement aqueous slurry of the present inventionis that it has a retarded time of initial set, and therefore remainspumpable for a relatively long period of time and a relatively longperiod of time passes before it thickens, yet it will attain a final setof some considerable strength within a reasonable length of time so thatthe well-drilling crew is not unduly delayed, but can get back to workand proceed to continue drilling the well bore, or to perforate thecasing and/or cement with the usual gun perforating tools known to theart. All types of said list of sulfoalkylcelluloses and all salts of thesame have sufficient set retarding and thickening time extendingproperties to be used commercially in the practice of the presentinvention, and when carefully prepared so that a relatively high degreeof substitution has occurred with relatively low amounts of degradationof the cellulose molecules, a secondary effect is achieved, which, whilenot as important as the first mentioned effect of delaying the time ofinitial set and extending the thickening time of the cement, is also ofconsiderable value in cementing oil wells, namely, the aqueous cementslurry containing the minor but effective amount of one of said list ofsulfoalkylcelluloses and all salts of the same has a reduced tendency tolose water to porous formations across the surface of which it must passin going to its intended position in the well. Many failures in priorart oil well cementing jobs, which have been accredited to the prematuresetting of the cement, are thought to be caused actually by theformation dehydrating the cement slurry, thereby rendering the cementimmobile before it reaches the desired position. As the practice ofusing Scrapers to clean the mud off the well walls to obtain a bettercementformation bond becomes more frequently used, the better theformations will absorb water from the cement slurry causing it not onlyto plug the annulus between the casing and the wall of the well, butalso to have insuicient water for normal hydration upon setting, and thegreater will become the realization of the need for low water-losscements.

Everything which is said applying to natural formation: in wells appliesalso in some degree to man-made formations being grouted, and the wordformation as used herein is regarded as generic to natural earthformations, geological formations, and man-made formations such asstructures.

In the prior art of squeeze cementing in wells and in forcing grout intothe cracks and crevices in fractured foundations or the like, it hasbeen the practice to employ as a breakdown agent, water or drilling mud,which is forced ahead of the aqueous hydraulic cement slurry into theformation to split the same and enlarge the fractures or cracks to befilled, because if ordinary hydraulic cement aqueous slurry wereemployed it would lose water to the formation or foundation so rapidlythat the cement slurry would start to set before much penetration hasbeen effected. When a relatively low water-loss hydraulic cement aqueousslurry is employed, the amount of breakdown agent can be greatlyreduced, or entirely eliminated, because the low water-loss cementslurry will penetrate to much greater distances before losing sufficientwater to be caused to set by this dehydration. When squeeze cementing inoil wells is involved, in which it is desired to force a thin disk orlayer of these cement slurries out into a natural earth formation alongpre-existing or pressuremade fractures. in order to separate an oil sandfrom some other sand at the general vicinity where the oil wellintersects the same, it is especially advantageous to use a relativelylow water-loss cement slurry as breakdown agent because then less wateris likely to be absorbed by the oil formation where it might cause areduction in the present or future amount of production of oil. Someoil-bearing formations contain bentonitic materials which swell whenthey encounter water, and if excess water is injected into suchformations, the swelling of the bentonitic material may prevent futureproduction of oil.

In the drawings:

Figure l is an elevational view with parts in section of apparatussuitable to carry out the processes of the present invention incompounding the hydraulic cement aqueous slurry and cementing a casingin a well, or grouting a formation.

Figure 2 is a cross sectional view of a portion of a weil in whichsqueeze cementing is being employed to place a cementitious horizontaldam out into the surrounding formation.

Figure 3 is a cross sectional view of a portion of a well in which aporous formation is plugged to prevent loss of circulation whiledrilling.

Figure l illustrates some of the processes devised by the presentinvention for cementing a casing 4 in a well 6 drilled in formation 7,or for grouting cracks or crevices in formation 7, it being understoodthat formation 7, instead of being a natural geological formation, maybe a man-made formation such as a foundation, dam, breakwater, or otherconcrete or masonry structure. While casing 4 could be placed in theopen bore 6 of the well, and the circulated drilling mud, `hydrauliccement aqueous slurry, or other uids in the bore 6 could be allowed toemerge around pipe 4 onto the surface of the formation 7 from theuncased bore 6, it is preferred to have at least one casing, soil pipe,or other pipe 8 secured in sealing Contact with formation 7, either byclose fit or by previous cementing 9. The pipe 8 is provided with acasing head 11 having a stuffing box or packing 12 forced into sealingcontact with casing 4 by some sort of follower 13. Casing head 11 alsois provided with an outlet pipe 14 which is preferably controlled by avalve 16 and which may discharge into a mud pit generally designated as17 through pipe 18.

A suitable amount of a suitable grade of hydraulic natural cement, suchas Portland cement, is fed from bin 19 through valve 21 into mixer 22and a minor but effective amount of a cellulose derivative comprisingacid sulfoalkyl cellulose ethers and salts of the same from the groupconsisting of acid a-methylsulfomethyl cellulose ether, acid sulfoethylcellulose ether, acid sulfopropyl cellulose ether, acid2-methyl-2-sulfoethyl cellulose ether, and acid ,a-dimethylsulfomcthylcellulose ether and salts of the same, for example sodium sulfoethylcellulose ether, say from 0.30 to 5 percent by weight of the dryhydraulic cement, for example, 0.5 percent by weight, is also fed intomixer 22 from the bin 23 controlled by valve 24. Of course this mixingin mixer 22 need not occur anywhere near the well, but could have takenplace any number of miles away and several months before, and then theready-mixed cement composition brought to thc well in sacks (not shown)or in a bulk cement truck (not shown). In any event the dry cementcomposition from mixer 22, or from cement sacks (not shown), is dumpedinto hopper 26 where it is picked up and mixed with a jet of. water fromtank 27 controlled by valve 28, or with a iet of drilling mud 29 frommud pit l7 through pipe 31 controlled by valve 32, the selected liquidbeing forced by pump 33 through jet pipe 34. The jet of liquid from 34picks up and mixes with the dry cement from hopper 26 and discharges thesame out opening 36, which could connect directly to casing 4. To insurethorough mixing, allow for inspection, and act as a surge reservoir, asuitable reservoir 37 is generally provided and l have found it usefulto have a baille in the same, over which the hydraulic cement aqueousslurry ows, and is then picked up by pipe 41 controlled by valve 42 fromwhich it may be pumped by pump 43 into casing 4 through pipe 44controlled by valve 46. Pipes 47 and 48 controlled by valves 49 and 5lrespectively, are both reserved for drilling mud 29 from mud pit 17,drawn through pipe 52 controlled by valve 53 when desired, or water fromtank 54 drawn through pipe 56 controlled by valve 57 when desired.

Casing 4 obviously generally consists of a number of pipes screwedtogether to form a single pipe and at its upper end it is provided withsome type of casing head 58. While not essential, it is useful to havea. pressure gauge 59 connected at some point in the system. The pressuregauge can be cut off by valve 6l.

While casing 4 could be cemented without the use of plugs 62 and 63simply by opening valves 16, 42, and 49, and pumping the hydraulicnatural cement aqueous slurry with pump 43 down inside of casing 4, outthe end thereof and up around the annular space 64 between bore 6 andcasing 4 on to the ground surface 66 around casing 4 (if no soil pipe 8is employed) this would not produce the best type of cementing availableas the interior of the casing 4 would be full of cement which would haveto be drilled out, and no pump pressure could be placed on the slurry.Whether soil pipe 8 is present for pressure control or not, it ispossible, when desired in the process, to close valve 42 and open eithervalve 53 or 57 and follow the cement with water 54 or drilling mud 29,and by counting the strokes of the pump and stopping the same andclosing valve 49 at the proper time to stop the cement water interfacebefore the drilling mud or water cornes out the bottom of casing 4, andthus cement without plugs 62 and 63 and still have casing 4 almost freeof cement. By providing soil pipe 8, casing head 11, flow line 18, valve16 and casing head 58, it is easy to place pressure on the slurry bythrottling or closing valve 16 when desired.

The two plug method illustrated, however', is preferred. Starting withplug 62 secured in casing head 58 between pipes 44 and 47 by set screw67 and plug 63 held as shown with set screws 68 and all of valves 42,53, 57, S1, 46, 49 and 16 closed, it is usual to first wash the annularspace 64 of well bore 6 with either drilling mud 29 adomos or water 54,in most cases drilling mud 29 being preferred, and to do so valve 53 or57 is opened, depending on whether drilling mud 29 or water is used,valve 16 is opened and valve 49 is opened and pump 43 is started,pumping the drilling mud (or water) through casing 4 up through annularspace 64 and out through pipe 18. At the same time casing 4 may be movedup and down through stuffing box 11, packing 12 being loosened byloosening follower 13, and casing 4 may, if desired, have securedthereto wall scraper elements generally designated as 70 which maycomprise annular rings 69 secured to casing 4, mounting more or lessradial wire bristles, rods or strips 71 which scrape the drilling mudcake olf the walls of well bore 6 in order to provide a good bondbetween the formation 7, the well, and casing 4. Any number of Scrapers69 may be provided and the movement of casing 4 may be great enough sothat the scraping of one set of scrapers 69 will overlap the scraping ofthe next adjacent set, and to allow this movement a flexible section ofpipe 72 may be provided in the line 73 from pump 43.

When the washing of the well and cleaning of the wallsl is sufficientlyaccomplished, pump 43 is stopped, and whichever of valves 53 and 57 wasopened is closed. The casing 4 at that time is spaced from the bottom ofthe hole 6 a distance less than the length of plug 62 plus a portion ofthe length of plug 63 but greater than the length of plug 62. Follower13 of stui`n`ng box 11 is adjusted to seal at l2 around casing 4. Valves16, 42 and 46 are open and set screw 67 is screwed away, releasing plug62, and pump 43 is started, pumping hydraulic cement aqueous slurry fromsump 74 of reservoir 37 into the space between plugs 62 and 63, forcinglplug 62 down casing 4 and out the end thereof into the position shown.The cement forces the plug out the end of casing 4 and proceeds up theannulus 64 forcing the mud or water ahead of it up annulus 64 and indoing so it may have to traverse an especially porous formation 76 whichwill take the water away from the aqueous slur ry in the absence of thesodium sulfocthyl cellulose 23r especially if the drilling mud has beenscraped from the surface of formation 76 by the Scrapers 7l. When thehydraulic natural cement aqueous slurry commences emerging from pipe 18,or when it is believed that it would emerge from pipe 18 or would reachthe desired elevation. in annulus 64 as soon as casing 4 were cleared ofcement, depending on the type of cementing job desired, then valve Sland one of valves 53 or S7 are opened, set screw 68 is loosened, andvalves 42 and 46 are closed, whereupon the water (or drilling mud)passes through pipe 48 into casing head 58, moving plug 63 down thecasing 4 until plug 63 rests on top of plug 62 but is unable to come outof the bottom of the casing and there-- fore plugs the end of casing 4,whereupon the pressure (as indicated by gauge 59) goes up as anindication of' what has happened, valve 51 is closed and pump 43 shutdown, leaving the annular space 64 full of cement and the inside ofcasing 4 full of water or drilling mud.

Any time during the entire pumping process from the time the cementreaches 76 until plug 63 seats on plug;

62 that it is desired to drive the hydraulic natural cement aqueousslurry into the more porous portions of the formation, such as formation76, it is only necessary to throttle pipe 18 by partially closing valve16, or, if de-Y sired, to close valve 16 completely for the desiredtimer which action will send up the pressure in the system to thedesired degree and force cement slurry into formation 76 if it will takethe same at the pressure.

The U, S. patents now in Class 166, Wells, Subclass 22,. Cementing orPlugging, disclose a number of other suit-- able cementing processeswhich may be employed in my invention.

Figure 2 is illustrative of a well 77 similar to Well 6 and equippedwith similar equipment in which a squeeze cementing job is employed toplace a cementitious hori zontal dam 78 out into the surroundingformation 79. As will be noted by the use of similar numbers, the equ1pment at the top of the well is all the same as in Figure 1 and isoperated in the same manner. Casing 4A differs from casing 4 somewhat,in that the intermediate portion of casing 4A is provided with a numberof radial holes 81 which holes are at rst covered by sleeve 83 held inplace by frangible pin 82. When plug 62 comes down the casing 4A aheadof the cement it catches in sleeve 83, breaks frangible pin 82 and opensopenings 81 to cement. This causes a jump of the indicator needle ofgauge 59 and at that time valve 16 can be closed for as long a period oftime as desired so that cement 78 can be forced away out into formation'79. When plug 63, which is followed by liquid 84 which may be water 54or drilling mud 29, reaches the top of plug 62 it plugs the interior ofcasing 4A, closing the holes 81. Incidentally, in both Figures l and 2,plugs 62 and 63 are made of wood, or some easily drillable plasticcomposition, and preferably sleeve 83 is made of some drillablematerial, such as aluminum or magnesium, so that after cement dike 78has set, the casing 4A can be drilled out to its original diameter anddrilling or other desired operations carried out through the same.

In Figure 2 the formations 86 and 87 may be more impervious thanformation 79, and the crack into which cement 78 is forced may haveoriginally been formed by the pressure on the aqueous slurry of pump 43with valve 16 closed, in which case formation 86 and all overlyingformations are raised or compressed enough to make room for cement 78.These formations 86, 87 and 79 may all be man-made, such as layers ofearth, concrete or masonry, as in a big dam or other foundation.

In Figure 3 is illustrated rotary drilling operations in which a well 88is being drilled with a iishtail bit 89 rotated at the end of a drillstring 91. Drill string 91 has a square section 92 known as a kellywhich is slidably and rotatably engaged with a square hole or bushing inrotary table 93, the drill bit being supported from eye 94 of rotaryswivel 96 by means of a hoisting tackle (not shown) and rotary table 93is rotated through gear 97 driven by motor 98. At the same time pump 43is pumping drilling mud 29 (see Figure l) through pipe 73, llexiblesection 72 and rotary swivel 96 down the inside of kelly 92 and drillstring 91 and out of the jet hole of bit 89. returning through annularspace 101 through soil pipe 8, valve 16 and pipe 18 into mud pit 17.Soil pipe 8 is provided with a stufling box 11A, which because the kellyis square has to have a rotatable portion 13A slidahly packing againstthe square sides of kelly 92. Such equipment is well known in the art ofdrilling wells, as shown by U. S. patents in Class 166, Wells, Subclassl5, Controllers; and Class 255, Earth Boring, Subclass 19A, Rotary,Blowout Preventers.

Motor 98 and rotary table 93 are supported by oor 102 of the usualrotary well drilling rig, the remainder of which drilling rig is notshown but is well known to those skilled in the art.

When rotary drilling, sometimes a cavernous formation 103 isencountered, containing passages 104 and 106, which may have anapparently unlimited capacity for taking up drilling mud in thedirection shown by the arrows. When such a formation is encountered,instead of directing ordinary drilling mud 29 in through pipe 52 andpumping the same down drill string 91 with pump 43, valve S3 is closed(see Figure 1) and valve 32 is opened, pump 33 is started, valve 28being closed, and drilling mud is jetted through 34 and mixed withhydraulic natural cement containing one of said list ofsulfoalkylcelluloses and all salts of the same which is discharged as anhydraulic cement aqueous mud containing slurry into 39 from which it ispicked up by pipe 41, valve 42 being open, and valves 53 and 57 closed,by pump 43 and pumped down drill string 91. At this time valve 16 may beclosed to increase the pressure forcing the slurry back into caverns 104and 106, but closing valve 16 may be unnecessary if caverns 104 and 106are already taking the drilling mud completely. Whenever the operator,because of rising pressure or the returning of slurries through pipe 18,decides that Caverns 104 and 106 are shut off and circulation has beenrestored, valve 42 is closed and valve S2 is opened, valve 16 now beingopened, and the rotary drilling continues in the usual manner withdrilling mud 39 from mud pit 17 washing the remains of the cementcontaining mud out of bore 101 and pipe 18. Obviously the pump 33 isshut down as soon as slurry 29 is no longer needed, and pipe 18 can bedeflected to another mud pit or dumping place (not shown) to avoid thecementitious mud returning to mud pit 17, until cement free mud returns,and then it can be deflected back to mud pit 17. These formations beingdrilled may be man-made as in a dam, or may be natA ural formationsencountered as in oil well drilling.

By hydraulic natural cement this invention intends to include allmixtures of lime, silica, and alumina, or of lime and magnesia, silicaand alumina and iron oxide (magnesia for example may replace part of thelime, and iron oxide a part of the alumina), as are commonly known ashydraulic natural cements. Hydraulic cements include hydraulic limes,grappier cements, puzzolan cements, and Portland cements. Puzzolancemcnts include slag cements made from slaked lime and granulated blastfurnace slag. Because of its superior strength Portland cement ispreferred among the hydraulic natural cements, but as the art of cementsrecognizes hydraulic natural cements as a definite class, and as resultsof value may be obtained with one of said list of sulfoalkylcellulosesand all salts of the same with any member of that class, it is desiredto claim all hydraulic natural cements. In addition to the ordinaryconstruction grades of Portland cement or other hydraulic naturalcements, modified hydraulic natural cements and Portland cementsdesignated as high-early-strength cement, heat-resistant cement, andslow-setting cement may be used in the present invention. The CondensedChemical Dictionary," 3rd edition, 1942, published by ReinholdPublishing Corporation, New York, N. Y., page 173, column 2, paragraph4, entitled, "Natural Cements," shows the preceding definition andclassification of hydraulic natural cements is recognized and followedby those skilled in the prior art.

In most oil well cementing and grouting operations it is generallydesirable to use neat cement for added strength, but obviously it isalways possible to add to the hydraulic natural cement, water, and oneof said list ot' sulfoalkylcelluoses and all salts of the same, anydesired amount of an inert granular filling material or aggregate suchas sand, ground limestone, or any of the other well known inert or evencementitious aggregates, as long as simple tests show the amount addeddoes not reduce the compressive strength after final set below thedesired value. For example, in plugging porous formations, bentonite orother clays are often added to hydraulic natural cement aqueousslurries, as taught by U. S. Patent 2,041,086 of May 19, 1936, or ironoxide or barium sulfate is added to make heavy cement. Any of theseaggregates can be added to the aqueous hydraulic natural cement slurryof the present invention in the usual proportions used in the prior art.

ln operations in previously uncased wells it is often desirable to useneat cement in the practice of the present invention, because inertfilling material may automatically become detached from the walls of thewell, and will tend to mix with and dilute the slurry to such an extentthat it is undesirable to add any filling material to the slurry beingforced into the well. It is customary in the prior art when cementing tomake simple tests as to time of set, compressive strength, etc., onsamples of the proposed mix.

The amount of water added to the cement of the present invention is notcritical, it being obvious that suficient Water should be added to forma pumpable slurry, and that when the slurry becomes pumpable no furtherwater need be added. One advantage of the slurry of the presentinvention when a relatively less degenerated one of said list ofsulfoalkylcelluloses and all salts of the same is used is that it is alow water-loss slurry, and therefore it is not necessary to add muchexcess water over the amount making the slurry pumpable as a reserve forexpected losses, which excess water might tend to reduce the finalcompressive strength of the cement.

lt has been found that all hydraulic natural cements, especiallyPortland and Portland-type cement aqueous slurries can be retarded insetting time, the time of thickening extended, and in some cases thewater-loss tendencies retarded, so that they meet all the aboverequirements for the satisfactory cementing of deep wells and likeoperations by the addition of a minor but effective amount of from about0.30 to 5% by weight of the dry hydraulic natural cement of one of thesaid list of acid sulfoalkyl cellulose ethers, or the metal, ammonium ororganic base, or other salts of one of said list of acid sulfoalkylcellulose ethers, without seriously affecting the other desirableproperties of the cement. lt is preferred at present to use the sodiumor potassium salts of one of said list of acid sulfoalkyl celluloseethers merely because these salts are readily available commercially andtherefore relatively inexpensive. However, good results will be obtainedusing any other alkali metal salt, such as the lithium, rubidium,caesium and other rare alkali metal salts, or the ammonium or organicbase salts of one of said list of acid sulfoalkyl cellulose ethers, allof which are water soluble. Typical organic base salts that can be usedare those derived from ammonia such as methyl amine, dimethyl amine andquaternary ammonium bases', also pyridine, morpholine and the like. Inaddition the alkaline earth metal salts such as the barium, calcium,strontium and magnesium, and the heavy metal salts such as the aluminum,iron, copper, lead, silver, mercury, nickel, and all other salts of oneof said list of acid sulfoalkyl cellulose ethers (which are probablyinsoluble in water but which hydrolyze in the hydraulic cement aqueousslurry which is an aqueous alkaline solution) are just as useful in thisinvention in the aqueous hydraulic cement slurry which is quitealkaline. Each ot' said list of acid sulfoalkyl cellulose ethers and allof their salts, whether such salt is formed in the aqueous hydraulicnatural cement slurry by hydrolysis of some water-insoluble salt, areall valuable in amounts of 5 percent or less, based on weight of drycement, in retarding the set of aqueous hydraulic natural cement slurry,especially at the temperature and pressure encountered in cementing awell, and in many instances one of said list of acid sulfoalkylcellulose ethers or salt will decrease the water loss from said aqueoushydraulic natural cement slurry to porous formations encountered in thewell.

While 0.30 to 5% of one of said list of acid sulfoalkyl cellulose ethersor their salts by weight of the dry hydraulic natural cement will givevaluable results, it has` been found that from 0.30 to 1% is the mostpreferred range in wells less than 14,000 feet deep and less than 300F., the use of 0.5% being particularly effective in such wells, and thepercentage above 1% being chiefly of value in still deeper and hotterWells.

Said list of acid sulfoalkyl cellulose ethers and their salts covers thesame however they may be produced. Of this list, sulfoethylcellulose(acid sulfoethyl cellulose ether), for example, can be made as describedin Example I of Dickey 2,422,000, June l0, 1947. By reacting theselected acid sulfoalkyl cellulose ether with the desired metal,ammonium, or organic base hydroxide, any desired salt can be produced.Scarth 2,570,492, October 9, 1951, teaches in column 3, lines 65 to 71,other means of forming the desired salts of such compounds.

The degree of substitution is not critical so long as the cellulosederivative is soluble or will hydrolyz in the hydraulic cement aqueousslurry. By degree of substitution is meant the average number ofsubstituted groups attached to the average anhydroglucose unit of thecellulose molecule, many of which are entirely unsubstituted, thesubstitution in the molecule being somewhat at random. Celluloseconsists of n such anhydroglucose units comprising residue X and 3hydroxyl groups -H. Any of the 3 hydroxyl groups may be substituted, sothe upper limit of substitution is said to be 3. lt is preferred to havethe degree of substitution of sulfoalkyl groups from 0.1 to 2.95, and ifalkyl groups are also present their degree of substitution is preferablyfrom 0.05 to 2.5.

The following formulas in which C is carbon, S sulfur, Na sodium, 0oxygen and H hydrogen, and X and n are as explained above, give thefollowing supposed average structure if a degree of substitution of oneis assumed:

acid a-methylsulfomethyl cellulose ether The sulfoalkyl group can alsobe:

-CHzCHaCHzSOsH sulfopropyl -CHroH-solH CH acid 2-methyl-2-sulfoethyl CH,ill-soin Hl acid, dimethylsulfomethyl The preparation of sulfoethylcellulose is also described in British Patent No. 470,994 (1937).

Portland cement is a mixture of complex silicates and aluminates ofcalcium containing excess lime. The setting or hardening is a result ofthe hydration or other chemical readjustments of the various components.Generally speaking, three periods in the set are recognized: initiaLfinal and hardening sets. The initial set normally occurs at ordinarytemperature in from one or two hours after the mixing, the nal set twoto tive hours later and the hardening continues for an indefinite timebut it is substantially complete in about 30 days.

The initial set is said to have occurred when a cement slurry has lostits plasticity to such a degree that the two pieces of a broken specimenwill not unite to form a homogeneous mass when placed in close contact.The individual grains of a cement slurry must remain undisturbed inintimate contact with each other for a time before the initial setoccurs in order to produce a coherent mass. Agitation during the latterpart of the period of initial set will prevent the cement from hardeningproperly to the desired homogeneous, coherent mass.

In order to form a perfect seal in cementing wells, it is necessary thatthe cement be placed before the initial set occurs and it is desirablethat it be placed and allowed to stand for a short period before theinitial set begins. With the equipment available, there is a limit tothe time in which it is possible to mix a cement and pump it into thebottom of the well and up around the casing to the location desired.

Another reason it is necessary to have the cement in place before theinitial set begins is that the viscosity rises as the settingprogresses. This increases the difticulty of pumping and is undesirablebecause of the added strain on the pumping equipment.

It is possible to retard the rate of set, within narrow limits, byincreasing the alumina content of the cement, but this method is notwidely used because of the high All cost of high alumina cements and thelimited effective range. The rate of set can be retarded also byincreasing the amount of Water present in the mix. However, above about35 to 50 percent water, based on the weight of dry cement, increasedamounts of water will result in weaker cement and there is no way ofknowing exactly how much dilution will result from water encountered inthe well. Addition of small amounts of gypsum, or calcium sulfate willresult in a retarded rate of set, but an excess will increase the rateand may cause the cement to disintegrate or be weakened. It is thereforehighly desirable that a retarded cement such as mine be available forcementing work.

The most convenient method of using one of said list ofsulfoalkyl-celluloses or salts of the same in cement is to run the sameand the hydraulic natural cement through a rotary mixer to produceintimate mixing and later add water to form a liuid slurry. However, thematerial selected from said list of sulfoalkylcelluloses or salts of thesame may be added directly to the cement and water at the time of mixingat the well, or the said material may be dissolved in the water withwhich the cement is mixed, with substantially the same result. Themethod of mixing is not critical as long as a somewhat unifonn mixtureis produced.

The rate of hydration or set of cement is ordinarily increased by anincrease in temperature. Since the bottom hole temperature in the wellmay be considerably higher than the atmospheric temperature, it isdesirable that a method such as I have described be available for use inthe cementing of oil wells. My method is effective at elevatedtemperatures as well as at ordinary atmospheric temperatures, becauseobviously a set retarding agent operative at atmospheric temperatureswill also retard the set at higher temperatures.

While it is not desired to limit the present invention by any theory ofoperation and while the scope and validity of the claims do not dependupon the validity of any theory 0f operation, it is believed helpful inunderstanding the invention to think of the one of said list ofsulfoalkylcelluloses or salts of the same temporarily absorbing so muchof the water that the Portland cement is only slowly table to obtainenough water to make its initial set, whereby the initial set of thecement is greatly retarded. Finally the Portland cement particles takethe Water away from the water soluble cellulose particles and attain aninitial and then a tinal set with suitable strength in the cement foruse in oil well cementing operations.

The prior art United States Patent 2,427,683 of September 23, 1947, toNorman C. Ludwig for "Retardcd Cement and Method of Making teaches thatthe setting time of an aqueous slurry of hydraulic cement (such asPortland cement and water) used in cementing a well can be retarded forabout three hours by adding trom 0.5 to 0.75 percent by weight of thedry cement of at least one of the group consisting ofcarboxymethylecllulose and salts of carboxymethylcellulose and/orhydroxyethylcellulose; acid carboxymethylcellulose. the sodium salts ofthe same, the alkali metal salts. the arnmonium salts and the othermetal salts such as the alumina, iron, copper, lead, silver, mercury,nickel and similar salts of carboxymethylcellulose, can all be usedbecause 'those which are not soluble in water will hydrolyze land becomesoluble in the hydraulic cement slurry which is always an alkalineaqueous slurry.

The materials suggested by said Ludwig patent are acidcarboxymethylcelluloscs and salts of the same and/ orhydroxyethylcellulose and no one of the said list ofsulfoalkylcelluloses or salts of the same is mentioned because none wereknown that would be suitable.

EXAMPLE I A neat Portland cement aqueous slurry having a density of 14pounds per gallon was tested Without any additive, and with 1 percent;0.75 percent; 0.50 percent; 0.25 percent and 0.10 percent respectivelyof the weight of the dry cement of sodium carboxyethylcellulose(abbreviated NaCEC in Table I below). To furnish a comparison a similarl percent of hydroxyethylcellulose (HEC) and l percent; 0.25 percent and0.05 percent of sodium carboxymethylcellulose (NaCMC) in the same slurryis also reported. Numbers 1 to 6, 11, l2, 14, 15, 18 to 20, 22 and 24 ofthese tests were first reported to the U. S. Patent Oiice in myapplication Serial No. 47,555 tiled September 2, 1948, in Table llthereof.

These tests include tests on aluminum carboxymethylcellulose (AlCMC),potassium cellulose sulfate (KCS),

according to the procedure described in API code 32 section XII (9).Throughout the remainder of this application these thickening times willbe referred to as Halliburton Thickening Times.

A Stanolind Pressure Thickening Time Tester was used lo determinethickening times of cement slurries under high pressure according to theprocedure set forth in API code 32 (9). These thickening times will bereferred to as Well Simulation Thickening Times in the remainder of thisapplication.

The statement set" in the table under Water-Loss means there was nowater-loss because the cement slurry had already set.

Table 1I Additive used Water-Loss (MLlMins.) Well Sinin- A Halliburton Mlation Thickening I Thickening Test N o. i Percent Time at Room At 180I, alter` Time,

Name by wt. of 180 F. Temp.. *w* `H` Hours to i cement (Hrs.) Initial l100 poises 1 hour Zhours 3 hours 4 hours at 12,000 ft.

0.9 20/0. 2 Set i 0.7 3.3 14/30 11/30 22/l.1 l 0.35 f, 35 15. 4 12/302512 aan 7777 1.0 2. 6 4/30 0.9 0. 7 9. 5 D. 6 0. 5 0. 4

sodium and barium oxycellulose (NaOC and BaOC), methylcellulose (MC),methyl hydroxyethylcellulose mixed ether (MHEC), sodium carboxymethyloxy cellulose mixed ether (NaCMOC), sodium sulfobenzylcellulose ether(NaSBC) and sodium sulfoethyl cellulose ether (NaSEC).

While numerous examples of the invention have been given, for purposesof illustration, the invention is not limited thereto.

Having described my invention, l claim:

l. A cement capable of forming a uid slurry when mixed with water andhaving thereafter an extended Table l i Additive Used Setting Time, Hrs.Compressive i Strength, p. s. t. Test No Viscosity oi' slurry y PercentRoom Room ylime wt. of Tempera- 200 F Tempera- 200 F.

dry ture ture cement 0 tluid 1 very viscous 1 slightly viscous.

t), 25 uld.

EXAMPLE. II

ln Table ll is reported the rcsults of tests of slurries of 40% water to60% Portland cement with the percent of additive being counted in theweight of the cement. For example, in test 26 no additive was used, intest 27 0.7% by weight of the cement of sodium sulfoethylcellulose(NaSEC) was used. and in test 28 0.35% by weight of the cement of NaSECand the same amount oi sodium carhoxymethyl hydroxyethyl cellulose mixedether was used.

Thickening times of cement slurries were measured at atmosphericpressure in a Halliburton consistorneter cement mixed with 0.3 to 5percent by weight of said dry cement of a water soluble cementthickening time extending agent selected from the group consisting ofacid a-methylsulfomethyl cellulose ether, acid sulfoethyl celluloseether, acid sulfopropyl cellulose ether, acid 2-methyl-2-sulfoethylcellulose ether, and acid ,a-dimethylsulfomethyl cellulose ether, andwater soluble salts of the same.

3. A cement capable of forming a fluid slurry when mixed with Water andhaving thereafter an extended thickening time, consisting essentially ofdry Portland cement mixed with 0.3 to 5 percent by weight of said drycement of water soluble acid sulfoethyl cellulose ether.

4. A cement capable of forming a uid slurry when mixed with water andhaving thereafter an extended thickening time, consisting essentially ofdry Portland cement mixed with 0.3 to 5 percent by weight of said drycement of water soluble sodium sulfoethyl cellulose ether.

5. A hydraulic cement slurry having an extended thickening time,consisting essentially of a dry hydraulic natural cement mixed with 0.3to 5 percent by weight of said dry cement of a water soluble cementthickening time extending agent selected from the group consisting ofacid at-methylsulfomethyl cellulose ether, acid sulfoethyl celluloseether, acid sulfopropyl cellulose ether, acid 2-methyl-2-sulfoethylcellulose ether, and acid ,adimethylsulfomethyl cellulose ether, andwater soluble salts of the same, and `sufficient water to produce apumpable slurry.

6. A hydraulic cement slurry having an extended thickening time,consisting essentially of dry Portland cement mixed with 0.3 to 5percent by weight of said dry cement of a water soluble cementthickening time extending agent selected from the group consisting ofacid a-methylsulfomethyl cellulose ether, acid sulfoethyl celluloseether, acid sulfopropyl cellulose ether, acid 2- methyl-Z-sulfoethylcellulose ether, and acid a,a-dimethylsulfomethyl cellulose ether, andwater soluble salts of the same, and suicient water to produce apumpable slurry.

7. A hydraulic cement slurry having an extended thickening time,consisting essentially of dry Portland cement mixed with 0.3 to 5percent by weight of said dry cement of water soluble acid sulfoethylcellulose ether, and sucient water to produce a pumpable `slurry.

8. A hydraulic cement slurry having an extended thickening time,consisting essentially of dry Portland cement mixed with 0.3 to 5percent by weight of said dry cement of water soluble sodium sulfoethylcellulose ether, and sufficient water to produce a pumpable slurry.

References Cited in the file of this patent UNITED STATES PATENTS2,188,767 Cannon et al. Jan. 30, 1940 2,427,683 Ludwig Sept. 23, 19472,583,657 Lea et al. Jan. 29, 1952 OTHER REFERENCES Identification ofOrganic Compounds, by Shriner and Fuson, 1948 edition, New York: JohnWiley & Sons, Inc., pages 66 and 67.

Mellors Modern Inorganic Chemistry, by Parkes and Mellor, 1939 edition,London: Longmans, Green & Co., pages 213, 220, 221.

1. A CEMENT CAPABLE OF FORMING A FLUID SLURRY WHEN MIXED WITH WATER ANDHAVING THEREAFTER AN EXTENDED THICKENING TIME, CONSISTING ESSENTIALLY OFA DRY HYDRAULIC NATURAL CEMENT MIXED WITH 0.3 TO 5 PERCENT BY WEIGHT OFSAID DRY CEMENT OF A WATER SOLUBLE CEMENT THICKENING TIME EXTENDINGAGENT SELECTED FROM THE GROUP CONSISTING OF ACID A-METHYLSULFOMETHYLCELLULOSE ETHER, ACID SULFOETHYL CELLULOSE ETHER, ACID SULFORPROPYLCELLULOSE ETHER, ACID 2-METHYL-2-SULFOETHY CELLULOSE, ETHER, AND ACID A,A-DIMETHYLSULFOMETHYL CELLULOSE ETHER, AND WATER SOLUBLE SALTS OF THESAME.